$300 is a pretty good deal for one of these radios. They're quite complex.
That said, you might still lean on them a little harder on the price. I've read quite a few cases here and elsewhere of Honda splitting parts/labor or covering all parts/no labor for this problem. And it does seem as though they've gotten it figured out--there don't seem to be as many problems with the units in '04-'05. Maybe they'll help you out, maybe they won't, but it's worth calling around and trying a few different dealers.
Good luck!
PS-it's also worth mentioning that even Honda has quality problems. We've seen evidence of that here on the site. But it doesn't seem as though they'll leave you stranded anywhere, in general. As stevel or anysia (don't remember which) once pointed out to me, there aren't any stories on here of someone having one of them towed. Hondas are still some of the most reliable cars out there that you can buy. Sure, a light being such an expensive repair is frustrating, but at least you aren't shelling out $50+ for a tow.
